CHEMICAL CHANGES Flashcards
What is an acid?
A substance that forms aqueous solutions with a pH below 7
What ions do acids form in water?
H+ ions
What is a base?
A substance with a pH above 7 (e.g. an alkali)
What ions do alkalis form in water?
OH- ions
What is the reaction between acids and bases called?
Neutralisation
What is the word equation for the reaction between acids and bases?
Acid + base —> salt + water
What are some examples of bases?
Metal oxides
Metal hydroxides
Metal carbonates
What do acids and metal oxides form?
Salt and water
What do acids and metal hydroxides form?
Salt and water
How do you form the salts name?
Metal + acid(ide)
What do acids and metal carbonates form?
Salt and water and carbon dioxide
How do you make soluble salts?
React an acid and insoluble base
What is the reactivity series?
Potassium
Sodium
Lithium
Calcium
Magnesium
CARBON
Zinc
Iron
HYDROGREN
Copper
What does it mean when a metal is reactive?
How quickly they can lose electrons to form positive ions
What is formed when an acid and metal react?
Salt and hydrogen
What is formed when a metal reacts with water?
Metal hydroxide and hydrogen
What is oxidation?
Gain of oxygen (loss of electrons)
What is reduction?
Loss of oxygen (gain of electrons)
How can metals be extracted from their metal oxides by reduction using carbon?
Carbon replaces the metal it is more reactive than in the equation (takes away its oxygen)
What is a redox reaction?
When oxidation and reduction are happening at the same time
What is the rule for displacement reactions?
A more reactive metal will displace a less reactive metal from its compound
Losing and gaining of electrons shown in an equation?
If a metal reacts with something it gains positive ions and loses two electrons so = Fe –> Fe2+ +2E-
If a metal is less reactive it loses positive ions and gains two electrons so
= Cu2 +2E- –> Cu
In a displacement reaction, which reactant is being oxidised?
The metal
In a displacement reaction, which reactant is being reduced?
The metal compound
What is an electrolyte?
A molten or dissolved ionic compound
What happens during electrolysis?
An electric current is passed through an electrolyte
The ions then move towards this and react causing the compound to decompose
What happens to the positive ions in electrolysis?
They move towards the negatively charged cathode and gain electrons (they are reduced)
What happens to the negative ions in electrolysis?
They move towards the positively charged anode and lose electrons (they are oxidised)
Why cant an ionic solid be electrolysed?
Because the ions are in fixed positions and cant move
Why can molten ionic compounds be electrolysed?
Because the ions can move freely and conduct electricity
What happens during electrolysis of molten ionic solids?
Positive metal ions are reduced to the element at the cathode
Negative metal ions are oxidised to the element at the anode
How are metals extracted from their ores (metal oxides) using electrolysis? aluminium and oxygen
Positive Al3+ ions are attracted to the cathode where they pick up 3 electrons and turn into aluminium atoms
Negative O2- ions are attracted to the anode where they lose 2 electrons and then combine to form oxygen (O2)
What ions do non-metals form?
Negative ions
What ions do metals form?
Positive ions
In aqueous solutions (during electrolysis) what other ions are present?
Hydrogen ions (H+)
Hydroxide ions (OH-)
What happens at the cathode during electrolysis in aqueous solutions? H
Hydrogen gas will be produced if the metal is more reactive than hydrogen (if not then a solid layer of the pure metal is produced)
What happens at the anode during electrolysis in aqueous solutions?
If OH- and halide ions are present then molecules of chlorine bromine or iodine will be formed
If not then the OH- ions are discharged and oxygen is formed
